Process for the preparation of a polyolefin, and a catalyst for this process

ABSTRACT

Polyolefins having a broad molecular weight distribution are obtained in a very high yield even using, as the catalyst, a product from the reaction of a magnesium alcoholate with titanium tetrachloride, if the reaction between the magnesium alcoholate and the titanium tetrachloride is carried out at a relatively low temperature and the reaction mixture is then heated to a fairly high temperature in order to split off alkyl chlorides.

Processes are known for the preparation of polyolefins by means ofcatalysts which are formed by reacting magnesium alcoholates and/orcomplex magnesium alcoholates with transition metal halides. (GermanAuslegeschriften Nos. 1,795,197 and 1,957,679 and GermanOffenlegungsschrift No. 2,000,566).

In one case, a temperature range of 0° to 200° C. is recommended for thereaction of the magnesium compound and the chlorine-containing titaniumcompound, but the upper temperature limit should be so chosen that nodecomposition products are formed. In addition to the high activity ofthe polymerization catalysts, it is mentioned as a special advantagethat it is possible to prepare ethylene homopolymers andethylene/α-olefin copolymers which have a narrow molecular weightdistribution (German Auslegeschriften Nos. 1,795,197 and 1,957,679).

In another case, the reaction of the metal alcoholate with thetransition metal compound is carried out in the presence or absence ofan inert diluent at temperatures of 40° to 210° C.; the duration of thereaction is, in general, between 5 and 240 minutes (GermanOffenlegungsschrift No. 2,000,566). An express warning is given againsta longer reaction time, since it is alleged to cause an impairment ofthe properties of the catalyst. In this publication too, it is mentionedas an advantage of the catalysts that they have a high activity and thatit is possible to prepare polyolefins which have a narrow molecularweight distribution. A catalyst which is obtained by reacting magnesiumethylate with vanadium tetrachloride and which produces a polyethylenehaving a broad molecular weight distribution is described at the sametime. However, vanadium compounds have the great disadvantage that, incontrast with titanium compounds, they are extremely toxic. Productscontaining vanadium compounds can, therefore, only be employed to alimited extent. In addition, high costs are incurred in working up thecatalyst mother liquors if vanadium compounds are employed in industrialpolymerization processes.

The problem was therefore presented of finding polymerization catalystsbased on a magnesium alcoholate, by means of which polyolefins having abroad molecular weight distribution can be prepared in a high yield.

It has now been found that polyolefins having a broad molecular weightdistribution can be obtained in a very high yield even using theproducts of the reaction of magnesium alcoholates with titaniumtetrachloride, if the reaction between the magnesium alcoholate and thetitanium tetrachloride is carried out at a relatively low temperatureand the reaction mixture is then subjected to a heat treatment at afairly high temperature in order to split off alkyl chlorides.

The invention relates therefore to a process for the polymerization of a1-olefin of the formula R⁴ CH═CH₂ in which R⁴ denotes hydrogen or analkyl radical having 1 to 10 carbon atoms, in the presence of a catalystcomposed of the product from the reaction of a magnesium alcoholate withtitanium tetrachloride (component A) and an organometallic compound ofGroups I to III of the periodic system (component B), which comprisescarrying out the polymerization in the presence of a catalyst in whichthe component A has been prepared by a procedure in which, in a firstreaction stage, a magnesium alcoholate has been reacted with titaniumtetrachloride in a hydrocarbon at a temperature of 50° to 100° C., thereaction mixture formed is subjected, in a second reaction stage, to aheat treatment at a temperature of 110° to 200° C., until no furtheralkyl chloride is split off, and the solid is then freed from solublereaction products by washing several times with a hydrocarbon.

The invention also relates, however, to the catalyst used for thisprocess and to its preparation.

A magnesium alcoholate is used for the preparation of the component A.This magnesium alcoholate can be a "simple" magnesium alcoholate of theformula Mg(OR)₂ in which R denotes identical or different alkyl radicalshaving 1 to 6 carbon atoms. Examples are Mg(OC₂ H₅)₂, Mg(OiC₃ H₇)₂,Mg(OnC₃ H₇)₂, Mg(OnC₄ H₉)₂, Mg(OCH₃)(OC₂ H₅) and Mg(OC₂ H₅)(OnC₃ H₇). Itis also possible to use a "simple" magnesium alcoholate of the formulaMg(OR)_(n) X_(m) in which X is halogen, (SO₄)_(1/2), OH, (CO₃)_(1/2),(PO₄)_(1/3) and Cl, R has the meaning mentioned above and n+m is 2.

It is also possible, however, to employ a "complex" magnesiumalcoholate. The term "complex" magnesium alcoholate describes amagnesium alcoholate which, as well as magnesium, contains at least onemetal of the 1st to 4th main group of the periodic system. The followingare examples of a complex magnesium alcoholate of this type: [Mg(OiC₃H₇)₄ ]Li₂ ; [Al₂ (OiC₃ H₇)₈ ]Mg; [Si(OC₂ H₅)₆ ]Mg; [Mg(OC₂ H₅)₃ ]Na;[Al₂ (OiC₄ H₉)₈ ]Mg; and [Al₂ (O-secC₄ H₉)₆ (OC₂ H₅)₂ ]Mg. The complexmagnesium alcoholates (alkoxo salts) are prepared by known methods(literature references: Meerwein; Ann. 455 (1927), page 234 and 476(1929), page 113; HoubenWeyl, Methoden der organischen Chemie ["Methodsof organic chemistry"], volume 6/2, page 30). The following examples ofthe preparation of the complex magnesium alcoholate may be mentioned:

1. Two metal alcoholates are allowed to act on one another in a suitablesolvent, for example

    2Al(OR).sub.3 +Mg(OR).sub.2 →[Al.sub.2 (OR).sub.8 ]Mg

2. Magnesium is dissolved in an alcoholic solution of a metal alcoholate

    2LiOR+Mg+2ROH→[Mg(OR).sub.4 ]Li.sub.2 +H.sub.2

3. Two metals are dissolved in alcohol simultaneously

    8ROH+Mg+2Al→[Al.sub.2 (OR).sub.8 ]Mg+4H.sub.2

The simple magnesium alcoholates, in particular Mg(OC₂ H₅)₂, Mg(OnC₃H₇)₂ and Mg(OiC₃ H₇)₂ are preferably used. The magnesium alcoholate isemployed in a pure form or fixed on a support.

The preparation of the component A is effected in two reaction stages atdifferent temperatures.

In the first reaction stage, the magnesium alcoholate is reacted withtitanium tetrachloride at a temperature of 50° to 100° C., preferably60° to 90° C., in the presence of an inert hydrocarbon and whilestirring. 1 to 5 moles of titanium tetrachloride are employed for 1 moleof magnesium alcoholate, preferably 1.4 to 3.5 mole of titaniumtetrachloride for 1 mole of magnesium alcoholate.

A suitable inert hydrocarbon is an aliphatic or cycloaliphatichydrocarbon, such as butane, pentane, hexane, heptane, isooctane,cyclohexane or methylcyclohexane, and an aromatic hydrocarbon, such astoluene or xylene; it is also possible to use a hydrogenated diesel oilor gasoline fraction which has been carefully freed from oxygen, sulfurcompounds and moisture.

The reaction time in the first stage is 0.5 to 8 hours, preferably 2 to6 hours.

A substantial replacement of the alkoxy groups of the magnesiumalcoholate by the chlorine atoms of the titanium tetrachloride takesplace in the first reaction stage. The reaction product obtained in thisstage is a solid which is insoluble in hydrocarbons and containsmagnesium and titanium, and titanium compounds which are soluble inhydrocarbons and contain chlorine and alkoxy groups.

In the second reaction stage, the resulting reaction mixture issubjected to a heat treatment at a temperature of 110° to 200° C.,preferably 110° to 160° C., while stirring. During this heat treatment,the titanium content of the hydrocarbon-insoluble solid increasesgreatly and alkyl chlorides are split off. It is assumed that thesoluble titanium alkoxychlorides are converted, by the splitting off ofalkyl chlorides, into condensed titanates which are insoluble inhydrocarbons and which are precipitated on the solid. The heat treatmentis carried out until no further alkyl chlorides are split off. As arule, a reaction time of 10 to 100 hours is required for this.

All the soluble reaction products are then removed by washing severaltimes with a hydrocarbon, and a solid which is insoluble in thehydrocarbon and which contains magnesium and titanium, is obtained; thiswill be designated component A.

The polymerization catalyst to be used in accordance with the inventionis prepared by bringing into contact with one another the component Aand an organometallic compound of Groups I to III of the periodic system(component B).

It is preferable to use organoaluminum compounds as the component B.Suitable organoaluminum compounds are organoaluminum compoundscontaining chlorine, the dialkylaluminum monochlorides of the formula R₂² AlCl or the alkylaluminum sesquichlorides of the formula R₃ ² Al₂ Cl₃in which R² can be identical or different alkyl radicals having 1 to 16carbon atoms. The following may be mentioned as examples: (C₂ H₅)₂ AlCl,(iC₄ H₉)₂ AlCl and (C₂ H₅)₃ Al₂ Cl₃.

It is particularly preferable to employ chlorine-free compounds as theorganoaluminum compounds. Compounds suitable for this purpose are,firstly, the products from the reaction of aluminum trialkyls oraluminum dialkylhydrides with hydrocarbon radicals having 1 to 6 carbonatoms, preferably the reaction of Al(iC₄ H₉)₃ or Al(iC₄ H₉)₂ H withdiolefins containing 4 to 20 carbon atoms, preferably isoprene. Aluminumisoprenyl may be mentioned as an example.

Secondly, chlorine-free organoaluminum compounds of this type arealuminum trialkyls AlR₃ ³ or aluminum dialkylhydrides of the formulaAlR₂ ³ H in which R³ denotes identical or different alkyl radicalshaving 1 to 16 carbon atoms. Examples are Al(C₂ H₅)₃, Al(C₂ H₅)₂ H,Al(C₃ H₇)₃, Al(C₃ H₇)₂ H, Al(iC₄ H₉)₃, Al(iC₄ H₉)₂ H, Al(C₈ H₁₇)₃,Al(C₁₂ H₂₅)₃, Al(C₂ H₅)(C₁₂ H₂₅)₂ and Al(iC₄ H₉)(C₁₂ H₂₅)₂.

It is also possible to employ mixtures of organometallic compounds ofGroups I to III of the periodic system, particularly mixtures ofdifferent organoaluminum compounds. The following mixtures may bementioned as examples: Al(C₂ H₅)₃ and Al(iC₄ H₉)₃, Al(C₂ H₅)₂ Cl andAl(C₈ H₁₇)₃, Al(C₂ H₅)₃ and Al(C₈ H₁₇)₃, Al(C₄ H₉)₂ H and Al(C₈ H₁₇)₃,Al(iC₄ H₉)₃ and Al(C₈ H₁₇)₃, Al(C₂ H₅)₃ and Al(C₁₂ H₂₅)₃, Al(iC₄ H₉)₃and Al(C₁₂ H₂₅)₃, Al(C₂ H₅)₃ and Al(C₁₆ H₃₃)₃, Al(C₃ H₇)₃ and Al(C₁₈H₃₇)₂ (iC₄ H₉) or Al(C₂ H₅)₃ and aluminum isoprenyl (the reactionproduct of isoprene with Al(iC₄ H₉)₃ or Al(iC₄ H₉)₂ H).

The component A and the component B can be mixed in a stirred kettle ata temperature of -30° C. to 150° C., preferably -10° to 120° C., beforethe polymerization. It is also possible to combine the two componentsdirectly in the polymerization kettle at a polymerization temperature of20° to 200° C. The addition of the component B can, however, also beeffected in two stages by pre-activating the component A with part ofthe component B at a temperature of -30° C. to 150° C. before thepolymerization reaction, and adding the remainder of the component B inthe polymerization reactor at a temperature of 20° to 200° C.

The polymerization catalyst to be used in accordance with the inventionis employed for the polymerization of 1-olefins of the formula R⁴ CH═CH₂in which R⁴ denotes hydrogen or an alkyl radical having 1 to 10 carbonatoms, for example ethylene, propylene, 1-butene, 1-hexene,4-methyl-1-pentene or 1-octene. It is preferable to polymerize ethyleneon its own or in the form of a mixture containing at least 70% by weightof ethylene and not more than 30% by weight of another 1-olefin of theabove formula. In particular, ethylene is polymerized on its own, or amixture containing at least 90% by weight of ethylene and not more than10% by weight of another 1-olefin of the above formula is polymerized.

The polymerization is carried out in a known manner in solution, insuspension or in the gas phase, continuously or discontinuously, in asingle stage or in several stages and at a temperature of 20° to 200°C., preferably 50° to 150° C. The pressure is 0.5 to 50 bar.Polymerization within the pressure range from 5 to 30 bar, which is ofparticular interest in industry, is preferred.

In this polymerization, the component A is used in a concentration,calculated as titanium, of 0.0001 to 1, preferably 0.001 to 0.5, mmoleof Ti per liter of dispersion medium or per liter of reactor volume. Theorganometallic compound is used in a concentration of 0.1 to 5 mmoles,preferably 0.5 to 4 mmoles, per liter of dispersion medium or per literof reactor volume. In principle, however, higher concentrations are alsopossible.

Suspension polymerization is carried out in an inert dispersion mediumwhich is customary for the Ziegler low-pressure process, for example inan aliphatic or cycloaliphatic hydrocarbon; butane, pentane, hexane,heptane, isooctane, cyclohexane or methylcyclohexane may be mentioned asexamples of such a hydrocarbon. It is also possible to use a gasoline orhydrogenated diesel oil fraction which has been carefully freed fromoxygen, sulfur compounds and moisture. The molecular weight of thepolymer is regulated in a known manner; it is preferable to use hydrogenfor this purpose.

As a result of the high activity of the catalyst to be used, the processaccording to the invention produces polymers having a very low contentof titanium and halogen and, therefore, extremely good values in thetest for color stability and corrosion. It also makes it possible toprepare polymers having a very broad molecular weight distribution; theMw/Mn values of the polymers are over 10.

A further decisive advantage of the process according to the inventioncan be seen in the fact that it makes it possible to prepare polymershaving molecular weights which differ very greatly, merely by varyingthe concentration of hydrogen. For example, polymers having molecularweights above 2 million are formed in a polymerization in the absence ofhydrogen, and polymers having molecular weights in the region of 30,000are formed at hydrogen contents of 70% by volume in the gas space.

The polymers can be fabricated at high throughput rates by the extrusionand blow-extrusion process to give hollow articles, tubes, cables andfilms which have smooth surfaces.

By virtue of a special structural composition, the hollow articles andbottles produced from the polyolefins obtained in accordance with theinvention are distinguished by a considerable lack of sensitivity tostress cracking.

Furthermore, the process according to the invention makes it possible toprepare, by suspension and gas phase polymerization, free-flowingpolymer powders having high bulk densities, so that they can beprocessed further directly to give shaped articles without a granulationstage.

EXAMPLES

In the examples which follow, a hydrogenated diesel oil fraction havinga boiling range of 130° to 170° C. is used for the preparation of thecatalyst and for the polymerization.

The titanium content of the catalysts is determined colorimetrically(literature reference: G. O. Muller, Praktikum der quantitativenchemischen Analyse ["Practical manual of quantitative chemicalanalysis"], 4th edition (1957), page 243).

The melt index MFI is determined as specified in DIN No. 53,735 (E).

The Mw/Mn values are determined from the fractionation data of a gelpermeation chromatograph at 130° C., using 1,2,4-trichlorobenzene as thesolvent and extraction medium.

The intrinsic viscosity is determined as specified in DIN No. 53,728,sheet 4, using an Ubbelohde viscometer, with decahydronaphthalene as thesolvent.

The density is determined as specified in DIN No. 53,479 and the bulkdensity as specified in DIN No. 53,468.

EXAMPLE 1 (a) Preparation of the component A

114.3 g of magnesium ethylate were dispersed, under a blanket of N₂, in1.5 l of a diesel oil fraction in a 3 l four-necked flask equipped witha dropping funnel, a KPG stirrer, a reflux condenser and a thermometer.332 g of titanium tetrachloride were added dropwise at 90° C. to thisdispersion in the course of 2 hours. The mixture was then warmed to 130°C. and was stirred at this temperature for 60 hours. A gentle stream ofN₂ was passed over the reaction mixture during the whole reaction timein order to expel gaseous reaction products, and this stream was thenpassed through a cold trap cooled with methanol/solid carbon dioxide.The evolution of gaseous reaction products was complete after 60 hours.116 g of a water-white liquid of the following composition: Cl=55% byweight, C=37% by weight and H=8% by weight were collected in the coldtrap. This was ethyl chloride. The reaction product was then washed withthe diesel oil fraction mentioned above, until the supernatant solutionno longer contained any titanium.

After drying, the solid (component A) had the following analyticalcomposition:

Ti 25.4% by weight

Mg 9.5% by weight

Cl 50.2% by weight

The Cl:Ti atomic ratio was 2.67.

(b) Pre-activation of the component A

19 g of the component A were made up to 190 ml with diesel oil, and 100ml of an aluminum triisobutyl solution containing 1 mole of Al(iC₄ H₉)₃per 1 l of solution were added at 20° C., while stirring. 45% by weightof the tetravalent titanium were reduced to titanium-(III) by thismeans.

(c) Polymerization of ethylene in suspension

100 l of diesel oil, 30 mmoles of aluminum triisobutyl and 8.7 ml of thedispersion described under (b) were charged to a 150 l kettle. 5 kg perhour of ethylene and sufficient H₂ to give an H₂ content of 55% byvolume in the gas space were then passed in, at a polymerizationtemperature of 85° C. After 6 hours the polymerization was terminated ata pressure of 25.3 bar, by releasing the pressure. The suspension wasfiltered and the polyethylene powder was dried by passing hot nitrogenover it.

28.7 kg of polyethylene were obtained. This corresponds to a catalystactivity of 50.4 kg of polyethylene/g of catalyst solid (component A) or9.5 kg of polyethylene/mmole of Ti. The polyethylene powder had an MFI190/5 of 0.54 g/10 minutes. The breadth of molecular weight distributionMw/Mn was 22 and the MFI 190/15/MFI 190/5 was 11.5. The density of thepowder was 0.955 g/cm³ and its bulk density was 0.49 g/cm³.

EXAMPLE 2 Polymerization of ethylene in suspension

100 mmoles of aluminum triisobutyl and 2.2 ml of the dispersiondescribed in Example 1(b) were charged to the kettle under the sameconditions as those described in Example 1(c). 5 kg per hour of ethylenewere then passed in at a polymerization temperature of 75° C. After 6hours the polymerization was terminated at a pressure of 24.8 bar, byreleasing the pressure. The suspension was filtered and the polyethylenepowder was dried by passing hot nitrogen over it. 27.9 kg ofpolyethylene were obtained. This corresponds to a catalyst activity of194 kg of polyethylene/g of catalyst solid or 36.5 kg ofpolyethylene/mmole of Ti. The polyethylene powder had an intrinsicviscosity of 2,400 ml/g; this corresponds to a molecular weight of 2million. Its bulk density was 0.45 g/cm³.

EXAMPLE 3 Polymerization of ethylene in suspension

100 mmoles of aluminum triisobutyl and 29 ml of the dispersion describedin Example 1(b) were charged to the kettle under the same conditions asthose described in Example 1(c). 4 kg per hour of ethylene andsufficient H₂ to give an H₂ content of 75% by volume in the gas spacewere then passed in at a polymerization temperature of 85° C. After 6hours the polymerization was terminated at a pressure of 25.6 bar, byreleasing the pressure. The suspension was filtered and the polyethylenepowder was dried by passing hot nitrogen over it. 23.6 kg ofpolyethylene were isolated. This corresponds to a catalyst yield of 12.4kg of polyethylene/g of catalyst solid or 2.3 kg of polyethylene/mmoleof Ti. The polyethylene had an MFI 190/5 of 105 g/10 minutes, anintrinsic viscosity of 110 ml/g, a density of 0.965 g/cm³ and a bulkdensity of 0.50 g/cm³. The breadth of molecular weight distributionMw/Mn was 25.

EXAMPLE 4 Copolymerization of ethylene and 1-decene in suspension

750 ml of hexane, 5 mmoles of aluminum isoprenyl and 2.9 mg of thecomponent A obtained in accordance with Example 1(b) were charged to a1.5 l steel autoclave. H₂ was then injected at 8 bar, and ethylene at 14bar, at a polymerization temperature of 85° C. The ethylene wassubsequently metered in at such a rate that a total pressure of 22 barwas maintained. 20 ml per hour of 1-decene were metered in at the sametime. The experiment was discontinued after 6 hours. The copolymer wasisolated by filtration and dried in a vacuum drying cabinet. 156 g ofcopolymer were obtained. This corresponds to a catalyst yield of 53.8 kgof polymer/g of catalyst solid or 10.1 kg of polymer/mmole of Ti. Theethylene/1-decene copolymer had a melt index MFI 190/5 of 0.68 g/10minutes and a density of 0.950 g/cm³.

EXAMPLE 5 Copolymerization of ethylene and 1-hexene in suspension

360 l of hexane, 360 mmoles of aluminum isoprenyl and 58 ml of thedispersion described in Example 1(b) were initially taken in a 500 lkettle. 17 kg/hour of ethylene, 2 l/hour of 1-hexene and sufficient H₂to set up an H₂ content of 45% by volume in the gas space were thenpassed in at a polymerization temperature of 85° C.

After 6 hours the polymerization pressure had risen to 8.2 bar, and thepolymerization was discontinued by releasing the pressure. The polymerpowder was isolated by filtration and was dried with hot nitrogen. 100.4kg of polymer were obtained. This corresponds to a catalyst yield of26.4 kg of polymer/g of catalyst solid or 5.0 kg of polymer/mmole of Ti.

The ethylene/1-hexene copolymer had a melt index MFI 190/5 of 0.9 g/10minutes, an MFI 190/15/MFI 190/5 ratio of 9.8, a density of 0.942 g/cm³and a bulk density of 0.42 g/cm³.

Bottles were produced from the powder on a blow-molding apparatus forbottles (extruder screw: D=60 mm). A very high output, 62 kg/hour, wasobtained at a screw speed of 40 r.p.m. The bottles had a very smoothsurface and had a very high resistance to stress cracking, over 1,000hours, in the Bell stress cracking test.

EXAMPLE 6 Copolymerization of ethylene and 1-butene in suspension

720 mmoles of aluminum triisobutyl and 58 ml of the dispersion describedin Example 1(b) were charged under the same conditions as thosedescribed in Example 5. 17 kg per hour of ethylene and 4 l per hour of1-butene were added at 65° C. Sufficient H₂ was passed in to give aconcentration of 40% by volume of the latter in the gas space. After 6hours the polymerization was discontinued at a final pressure of 6.7bar, by releasing the pressure.

The suspension was cooled to room temperature and the solid was isolatedby filtration and dried with hot N₂.

108.4 kg of product having an MFI 190/5 of 1.8 g/10 minutes, an MFI190/15/MFI 190/5 of 10.4, a density of 0.920 g/cm³ and a bulk density of0.30 g/cm³ were obtained. This corresponds to a catalyst yield of 28.5kg of copolymer/g of catalyst solid or 5.4 kg of copolymer/mmole of Ti.

EXAMPLE 7 Polymerization of ethylene in the gas phase

500 g of polyethylene powder (MFI 190/5=1.5 g/10 minutes; bulkdensity=0.45 g/cm³) were initially taken in a 20 l horizontal reactorequipped with a stirrer operating close to the wall. The reactor wasfreed from air by being evacuated several times and flushed for severalhours with ethylene and was then warmed to 80° C. 50 mmoles of aluminumtriisobutyl and 94.3 mg of the catalyst component A prepared inaccordance with Example 1(a) were added to the reactor.

400 g/hour of ethylene and sufficient hydrogen to keep the proportion ofhydrogen in the gas space at 30% by volume during the polymerizationwere passed in. The pressure rose to 15 bar during the reaction time.After 12.5 hours the polymerization was discontinued. 5.4 kg ofpolyethylene having an MFI 190/5 value of 0.6 g/10 minutes wereobtained. This corresponds to a catalyst yield of 52 kg ofpolyethylene/g of catalyst solid or 9.8 kg of polyethylene/mmole of Ti.

COMPARISON EXAMPLE A (a) Preparation of the component A

114.3 g of magnesium ethylate were dispersed, under a blanket of N₂, in1.5 l of a diesel oil fraction in a 3 l four-necked flask equipped witha dropping funnel, a KPG stirrer, a reflux condenser and a thermometer.332 g of titanium tetrachloride were added dropwise at 90° C. to thisdispersion in the course of 2 hours. The reaction product was thenwashed with the diesel oil fraction until the supernatant solution nolonger contained any titanium. After drying, the solid (component A) hadthe following analytical composition:

Ti 4.9% by weight

Mg 19.8% by weight

Cl 61.3% by weight.

(b) Pre-activation of the component A

98 g of the component A were suspended in sufficient diesel oil to givea volume of suspension of 190 ml, and 100 ml of an aluminum triisobutylsolution containing 1 mole of Al(iC₄ H₉)₃ per 1 l were added at 20° C.,while stirring. 52% by weight of the tetravalent titanium were reducedto titanium-(III) by this means.

(c) Polymerization of ethylene in suspension

100 l of hexane, 30 mmoles of aluminum triisobutyl and 14.5 ml of thesuspension described under (b) were charged to a 150 l kettle. 5 kg/hourof ethylene and sufficient H₂ to set up a hydrogen content of 30% byvolume in the gas space were then passed in at 85° C. After 6 hours thepolymerization was discontinued at a pressure of 4.6 bar, by releasingthe pressure. 29.6 kg of polyethylene were obtained. This corresponds toa catalyst yield of 6.1 kg/g of catalyst solid or 5.9 kg ofpolyethylene/mmole of Ti.

The product had an MFI 190/5 value of 1.6 g/10 minutes, an MFI190/15/MFI 190/5 value of 5.2, a density of 0.956 g/cm³ and a bulkdensity of 0.42 g/cm³. The product had a narrow molecular weightdistribution: Mw/Mn=4.7.

An output of 43 kg/hour was obtained at a screw speed of 40 r.p.m. whenprocessing the powder on the blow-molding apparatus for hollow articlesalso used in Example 5. The bottles had a rough surface, since meltfracture occurred when they were processed. The resistance to stresscracking of the bottles in the Bell test was 68 hours.

(d) Polymerization of ethylene in suspension

100 l of diesel oil, 30 mmoles of aluminum triisobutyl and 8.7 ml of thedispersion described under (b) were charged to a 150 l kettle. 5 kg perhour of ethylene and sufficient H₂ to give an H₂ content of 55% byvolume in the gas space were then passed in at a polymerizationtemperature of 85° C. After 6 hours the polymerization was terminated ata pressure of 20.4 bar, by releasing the pressure. The suspension wasfiltered and the polyethylene powder was dried by passing hot nitrogenover it.

28.2 kg of polyethylene were obtained. This corresponds to a catalystactivity of 9.6 kg of polyethylene/g of catalyst solid or 9.4 kg ofpolyethylene/mmole of Ti. The polymer powder had an MFI 190/5 of 28 g/10minutes. The breadth of molecular weight distribution Mw/Mn was 4.6 andthe MFI 190/15/MFI 190/5 was 5.4. The density of the powder was 0.960g/cm³ and its bulk density was 0.41 g/cm³.

EXAMPLE 8 (a) Preparation of the component A

114.3 g of magnesium ethylate were dispersed, under a blanket of N₂, in1.5 l of a diesel oil fraction in a 3 l four-necked flask equipped witha dropping funnel, a KPG stirrer, a reflux condenser and a thermometer.569 g of titanium tetrachloride were added dropwise at 90° C. to thisdispersion in the course of 2 hours. The mixture was then warmed to 130°C. and stirred at this temperature for 60 hours. A gentle stream of N₂was passed over the reaction mixture during the whole reaction time inorder to expel gaseous reaction products, and this stream was thenpassed through a cold trap cooled with methanol/solid carbon dioxide.The evolution of gaseous reaction products was complete after 60 hours.107 g of a water-white liquid of the following composition: Cl=55% byweight, C=37% by weight and H=8% by weight were collected in the coldtrap. This was ethyl chloride. The reaction product was then washed withthe diesel oil fraction until the supernatant solution no longercontained any titanium.

After drying, the solid (component A) had the following analyticalcomposition:

Ti 24.7% by weight

Mg 9.7% by weight

Cl 51.2% by weight.

The Cl:Ti atomic ratio was 2.80.

(b) Pre-activation of the component A

19.4 g of component A were made up to 190 ml with diesel oil, and 100 mlof an aluminum triisobutyl solution containing 1 mole of Al(iC₄ H₉)₃ per1 l were added at 20° C., while stirring. 47% by weight of thetetravalent titanium were reduced to titanium-(III) by this means.

(c) Polymerization of ethylene in suspension

100 l of diesel oil, 25 mmoles of aluminum triisobutyl and 8.0 ml of thedispersion described under (b) were charged to a 150 l kettle. 5 kg perhour of ethylene and sufficient H₂ to give an H₂ content of 55% byvolume in the gas space were then passed in at a polymerizationtemperature of 85° C. After 6 hours the polymerization was terminated ata pressure of 22.4 bar, by releasing the pressure. The suspension wasfiltered and the polyethylene powder was dried by passing hot nitrogenover it.

27.5 kg of polyethylene were obtained. This corresponds to a catalystactivity of 51.4 kg of polyethylene/g of catalyst solid or 10 kg ofpolyethylene/mmole of Ti. The polyethylene powder had an MFI 190/5 of0.94 g/10 minutes. The breadth of molecular weight distribution Mw/Mnwas 26 and the MFI 190/15/MFI 190/5 was 11.9. The density of the powderwas 0.956 g/cm³ and its bulk density was 0.47 g/cm³.

EXAMPLE 9 (a) Preparation of the component A

142.3 g of magnesium isopropylate were dispersed, under a blanket of N₂,in 1.0 l of a diesel oil fraction in a 3 l four-necked flask equippedwith a dropping funnel, a KPG stirrer, a reflux condenser and athermometer. 285 g of titanium tetrachloride were added dropwise at 75°C. to this dispersion in the course of 4 hours. The mixture was thenwarmed to 110° C. and was stirred at this temperature for 45 hours. Agentle stream of N₂ was passed over the reaction mixture during thewhole reaction time in order to expel gaseous reaction products, andthis stream was then passed through a cold trap cooled withmethanol/solid carbon dioxide. The evolution of gaseous reactionproducts was complete after 60 hours. 156 g of water-white liquid of thefollowing composition: Cl=45% by weight, C=46% by weight and H=8.9% byweight were collected in the cold trap. This was isopropyl chloride. Thereaction product was then washed with the diesel oil fraction mentionedabove, until the supernatant solution no longer contained any titanium.

After drying, the solid (component A) contained the following:

Ti 26.6% by weight

Mg 9.0% by weight

Cl 52.5% by weight.

The Cl:Ti atomic ratio was 2.67.

(b) Polymerization of ethylene in suspension

100 l of diesel oil, 100 mmoles of aluminum isoprenyl and 900 mg of thecatalyst solid described under (a) were charged to a 150 l kettle. 5 kgper hour of ethylene and sufficient H₂ to give an H₂ content of 55% byvolume in the gas space were then passed in at a polymerizationtemperature of 85° C. After 6 hours the polymerization was terminated ata pressure of 23.8 bar, by releasing the pressure. The suspension wasfiltered and the polyethylene powder was dried by passing hot nitrogenover it.

29.1 kg of polyethylene were obtained. This corresponds to a catalystactivity of 32.3 kg of polyethylene/g of catalyst solid or 5.8 kg ofpolyethylene/mmole of Ti. The polyethylene powder had an MFI 190/5 of0.36 g/10 minutes. The breadth of molecular weight distribution Mw/Mnwas 28 and the MFI 190/15/MFI 190/5 was 12.7. The density of the powderwas 0.954 g/cm³ and its bulk density was 0.39 g/cm³.

EXAMPLE 10 (a) Preparation of the component A

250.3 g of Na₂ [Mg(OC₂ H₅)₄ ](H. Meerwein and T. Bersin, Liebigs Annalender Chemie 476, 113 [1929]) were dispersed, under a blanket of N₂, in2.0 l of a diesel oil fraction in a 3 l four-necked flask equipped witha dropping funnel, a KPG stirrer, a reflux condenser and a thermometer.759 g of titanium tetrachloride were added dropwise at 80° C. to thisdispersion in the course of 4 hours. The mixture was then warmed to 145°C. and stirred at this temperature for 45 hours. A gentle stream of N₂was passed over the reaction mixture during the whole reaction time inorder to expel gaseous reaction products, and this stream was thenpassed through a cold trap cooled with methanol/solid carbon dioxide.The evolution of gaseous reaction products was complete after 60 hours.118 g of a water-white liquid of the following composition: Cl=55% byweight, C=37% by weight and H=8% by weight were collected in the coldtrap. This was ethyl chloride. The reaction product was then washed withthe diesel oil fraction mentioned above until the supernatant solutionno longer contained any titanium.

After drying, the solid (component A) had the following analyticalcomposition:

Ti 16.9% by weight

Mg 6.6% by weight

Cl 52.9% by weight

(b) Polymerization of ethylene in suspension

100 l of diesel oil, 30 mmoles of aluminum triisobutyl and 1,417 mg ofthe catalyst solid described under (a) were charged to a 150 l kettle. 5kg per hour of ethylene and sufficient H₂ to give an H₂ content of 65%by volume in the gas space were then passed in at a polymerizationtemperature of 85° C. After 6 hours the polymerization was terminated ata pressure of 21.7 bar, by releasing the pressure. The suspension wasfiltered and the polyethylene powder was dried by passing hot nitrogenover it. corresponds to a catalyst activity of 19.9 kg of polyethylene/gof catalyst solid or 7.1 kg of polyethylene/mmole of Ti. Thepolyethylene powder had an MFI 190/5 of 3.2 g/10 minutes. The breadth ofmolecular weight distribution Mw/Mn was 21 and the MFI 190/15/MFI 190/5was 10.5. The density of the powder was 0.955 g/cm³ and its bulk densitywas 0.49 g/cm³.

We claim:
 1. A process for the polymerization of ethylene or an olefinmixture comprising at least 70% by weight of ethylene and not more than30% by weight of a 1-olefin of the formula R₄ CH═CH₂ in which R⁴ denotesan alkyl radical having 1 to 10 carbon atoms, in the presence of acatalyst comprised of the product from the reaction of a magnesiumalcoholate of the formula Mg(OR)₂, in which R denotes identical ordifferent alkyl radicals having 1 to 6 carbon atoms, with 1 to 5 molestitanium tetrachloride for each mole of magnesium alcoholate (componentA) and an organometallic compound of Groups I to III of the periodicsystem (component B), which comprises carrying out the polymerization inthe presence of a catalyst in which the component A has been prepared bya procedure in which, in a first reaction stage, a magnesium alcoholatehas been reacted with titanium tetrachloride in a hydrocarbon at atemperature of 50° to 100° C., the reaction mixture formed is subjected,in a second reaction stage, to a heat treatment for a period of about 10to 100 hours at a temperature of 110° to 200° C., with evolution ofalkyl chloride until no further alkyl chloride is split off, and thesolid is then freed from soluble reaction products by washing severaltimes with a hydrocarbon.
 2. The process as claimed in claim 1, whereinthe component A is prepared by reacting, in the first reaction stage, acomplex magnesium alcoholate which, as well as magnesium, contains atleast one metal of the 1st to 4th main group of the periodic system,with titanium tetrachloride in a hydrocarbon at a temperature of 50° to100° C., subjecting, in a second reaction stage, the reaction mixturewhich has been formed to a heat treatment at a temperature of 110° to200° C. until no further alkyl chloride is split off, and then freeingthe solid from soluble reaction products by washing it several timeswith a hydrocarbon.
 3. A process according to claim 1, wherein theresulting polyethylene or ethylene/1-olefin copolymer has an Mw/Mn valuegreater than 10.